Role of long noncoding RNA in cardiac development

Role of long noncoding RNA in cardiac development
 

MIT biologists have now deciphered the structure of one type of long noncoding RNA (lncRNA) and used that information to figure out how it interacts with a cellular protein to control the development of heart muscle cells. This is one of first studies to link the structure of lncRNAs to their function.

In the new study, the researchers decided to investigate which regions of the 600-nucleotide RNA molecule are crucial to its function. "We knew Braveheart was critical for heart muscle cell development, but we didn't know the detailed molecular mechanism of how this lncRNA functioned, so we hypothesized that determining its structure could reveal new clues," author says.

To determine Braveheart's structure, the researchers used a technique called chemical probing, in which they treated the RNA molecule with a chemical reagent that modifies exposed RNA nucleotides. By analyzing which nucleotides bind to this reagent, the researchers can identify single-stranded regions, double-stranded helices, loops, and other structures.

This analysis revealed that Braveheart has several distinct structural regions, or motifs. The researchers then tested which of these motifs were most important to the molecule's function. To their surprise, they found that removing 11 nucleotides, composing a loop that represents just 2 percent of the entire molecule, halted normal heart cell development.

The researchers then searched for proteins that the Braveheart loop might interact with to control heart cell development. In a screen of about 10,000 proteins, they discovered that a transcription factor protein called cellular nucleic acid binding protein (CNBP) binds strongly to this region. Previous studies have shown that mutations in CNBP can lead to heart defects in mice and humans.

Further studies revealed that CNBP acts as a potential roadblock for cardiac development, and that Braveheart releases this repressor, allowing cells to become heart muscle.

Scientists have not yet identified a human counterpart to the mouse Braveheart lncRNA, in part because human and mouse lncRNA sequences are poorly conserved, even though protein-coding genes of the two species are usually very similar. However, now that the researchers know the structure of the mouse Braveheart lncRNA, they plan to analyze human lncRNA molecules to identify similar structures, which would suggest that they have similar functions.

"We're taking this motif and we're using it to build a fingerprint so we can potentially find motifs that resemble that lncRNA across species," senior author says. "We also hope to extend this work to identify the modes of action of a catalog of motifs so that we can better predict lncRNAs with important functions."

http://news.mit.edu/2016/linking-rna-structure-and-function-cell-fate-0908

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